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Expose DMABUF functionality to userspace through the uverbs interface, enabling InfiniBand/RDMA devices to export PCI based memory regions (e.g. device memory) as DMABUF file descriptors. This allows zero-copy sharing of RDMA memory with other subsystems that support the dma-buf framework. A new UVERBS_OBJECT_DMABUF object type and allocation method were introduced. During allocation, uverbs invokes the driver to supply the rdma_user_mmap_entry associated with the given page offset (pgoff). Based on the returned rdma_user_mmap_entry, uverbs requests the driver to provide the corresponding physical-memory details as well as the driver’s PCI provider information. Using this information, dma_buf_export() is called; if it succeeds, uobj->object is set to the underlying file pointer returned by the dma-buf framework. The file descriptor number follows the standard uverbs allocation flow, but the file pointer comes from the dma-buf subsystem, including its own fops and private data. When an mmap entry is removed, uverbs iterates over its associated DMABUFs, marks them as revoked, and calls dma_buf_move_notify() so that their importers are notified. The same procedure applies during the disassociate flow; final cleanup occurs when the application closes the file. Signed-off-by: Yishai Hadas <yishaih@nvidia.com> Signed-off-by: Edward Srouji <edwards@nvidia.com> Link: https://patch.msgid.link/20260201-dmabuf-export-v3-2-da238b614fe3@nvidia.com Signed-off-by: Leon Romanovsky <leon@kernel.org>